VOID STRUCTURE AND PROPERTIES OF NONEQUILIBRIUM BOUNDARIES

Within the interval between the equilibrium state of a grain boundary in a metal and the non-equilibrium state of the physical contact betwe en two surfaces in a powder pressed compact. there are many non-equili brium boundaries of common type with an energy of gamma(gb)<gamma(if)< 2 gamma(s). Boundary voids and the excessive free volume play a key ro le in formation of the compact structure. A term of ''latent'' grain-b oundary porosity has been introduced which is attributed to the ''weak ened'' interatomic bunds within the region of scattered free spaces: t his porosity, along with common planar porosity caused by disrupted in teratomic bonds within formed pores. determines the properties of boun daries. A theoretical expression has been determined for calculating t he strength of hollow boundaries. A qualitative model has been propose d explaining the variations in the mobility of common boundaries durin g migration depending on the impurities concentration. A rapidly proce eding mechanism of migration of strongly non-equilibrium and stressed boundaries has been offered. The low viscosity of boundaries is due to high planar porosity.